Messages in this thread | | | Date | Tue, 5 Jun 2012 15:00:59 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH 0/6] x86/cpu hotplug: Wake up offline CPU via mwait or nmi |
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On Tue, Jun 05, 2012 at 11:37:21PM +0200, Peter Zijlstra wrote: > On Tue, 2012-06-05 at 14:29 -0700, Paul E. McKenney wrote: > > OK, I'll bite... Why not just use CPU hotplug to expel the timers? > > Currently? Can you say: 'kstopmachine'?
So if CPU hotplug (or whatever you want to call it) stops using kstopmachine, you are OK with it?
> But its also a question of interface and naming. Do you want to have to > iterate all cpus in your isolated set, do you want to bring them down > far enough to physically unplug. Ideally no to both.
For many use cases, it is indeed not necessary to get to a point where the CPUs could be physically removed from the system. But CPU-failure use cases would need the CPU to be fully deactivated. And many of the hardware guys tell me that the CPU-failure case will be getting more common, though I sure hope that they are wrong.
> If you don't bring them down far enough to unplug, should you still be > calling it hotplug?
I am not too worried about what it is called. Though "banish to monastery" would probably be going too far in the other direction.
> Ideally I think there'd be a file in your cpuset which if opened and > written to will flush all pending bits (timers, workqueues, the lot) and > return when this is done (and maybe provide O_ASYNC writes to not wait > for completion).
The mobile guys probably are not too worried about bulk operations yet because they don't have that many CPUs, but it might be useful elsewhere.
Thanx, Paul
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